[PATCH], PR 71294, Fix -O3 -fstack-protector bug on PowerPC power8

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

It might be argued that this is a reload bug (since it runs on LRA), but
sometimes it is simpler to place a simpler work around in the machine dependent
code.  If the maintainers decide that it should be fixed in reload instead of
via this patch, that is fine.

PR 71294 involves vectorization where the compiler is forming a V2DI vector
from 2 DI elements.  The elements are the same value (a stack address), so the
register allocator copies the address over to the VSX register file, and does
an XXPERMDI.  Because of the -fstack-protector, frame addresses are modified,
and become an ADD operation, and the direct move fails.

I added a splitter for DImode so that if a virtual register or frame address
register was attempted to be splatted to the VSX register file, it would copy
the value to a pseudo register, and do a direct move on that.

I have done a bootstrap and regression test with these patches and there were
no regressions.  Are the patches ok to install in the trunk?

[gcc]
2016-05-26  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/71294
	* config/rs6000/predicates.md (virtual_or_frame_reg_operand): New
	predicate to return true if the operand is a virtual or frame
	register.
	* config/rs6000/vsx.md (move splat splitters): Add splitters to
	copy a frame related pointer into a new pseudo register during the
	first split pass, so that we don't confuse the register allocator.

[gcc/testsuite]
2016-05-26  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/71294
	* g++.dg/pr71294.C: New test.


-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797

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